• Karsten Blees's avatar
    trace: add trace_performance facility to debug performance issues · 09b2c1c7
    Karsten Blees authored
    Add trace_performance and trace_performance_since macros that print a
    duration and an optional printf-formatted text to the file specified in
    environment variable GIT_TRACE_PERFORMANCE.
    
    These macros, in conjunction with getnanotime(), are intended to simplify
    performance measurements from within the application (i.e. profiling via
    manual instrumentation, rather than using an external profiling tool).
    
    Unless enabled via GIT_TRACE_PERFORMANCE, these macros have no noticeable
    impact on performance, so that test code for well known time killers may
    be shipped in release builds. Alternatively, a developer could provide an
    additional performance patch (not meant for master) that allows reviewers
    to reproduce performance tests more easily, e.g. on other platforms or
    using their own repositories.
    
    Usage examples:
    
    Simple use case (measure one code section):
    
      uint64_t start = getnanotime();
      /* code section to measure */
      trace_performance_since(start, "foobar");
    
    Complex use case (measure repetitive code sections):
    
      uint64_t t = 0;
      for (;;) {
        /* ignore */
        t -= getnanotime();
        /* code section to measure */
        t += getnanotime();
        /* ignore */
      }
      trace_performance(t, "frotz");
    Signed-off-by: default avatarKarsten Blees <[email protected]>
    Signed-off-by: default avatarJunio C Hamano <[email protected]>
    09b2c1c7
trace.c 9.76 KB